What’s Your Threshold Threshold? Don’t Set It Too High

For the best results, incorporate some threshold runs into your training schedule. But not too many. Photo: www.shutterstock.com

Why it’s easy to get too much of a good thing with anaerobic threshold training.

There have always been competing training philosophies in the sport of distance running. At the most general level of classification, there are two training schools: the high-mileage school and the high-intensity school. Representatives of the high-mileage school believe runners should do most of their training at an easy pace — but lots of it. Representatives of the high-intensity school believe that it’s better to run less but run hard.

While most competitive runners continue to favor the high-mileage approach, exercise scientists have lately found more merit in the high-intensity school. This belief is based on short-term studies in which the addition of high-intensity workouts to the training schedule of volunteers seems to improve their performance. I believe these studies need to be taken with a grain of salt, however, because they do not closely represent the real-world training environment of competitive runners.

It’s very difficult to conduct truly valid scientific studies on the general effectiveness of specific training practices. The reason is that it’s hard to adequately control the training of large groups of runners over extended periods of time. Some of the best studies on the effects of specific training practices in runners have been conducted by a team of researchers at the University of Madrid, Spain. One particular study by this team provides support for the philosophy that distance runners should do most of their training at an easy pace.

The team divided 10 high-level male runners into two groups. At the beginning of the study period, all 10 runners completed a 10.4-kilometer time trial and their times were recorded. Over the next five months, the runners in the two groups trained identically except for one key difference. The members of one group did two threshold runs per week, while the members of the other group did just one. Their total training mileage, speed training schedules, and strength training regimens were the same. The only difference was that the members of one group did more threshold running and less easy running than the members of the second group.

At the end of the study period, all 10 runners repeated the 10.4-km time trial. The members of the “threshold” group improved their time by 2:01, on average, while those in the “easy” group improved by 2:37. Statistical analyses revealed that such a large discrepancy was extremely unlikely to occur by chance. Therefore the researchers concluded that a training program in which 81 percent of running is easy, 10.5 percent is done at threshold pace, and 8.5 percent is done at speeds exceeding race pace is more effective than an equal-mileage program in which only 67 percent of running is easy, 24.5 percent is at threshold pace, and 8.5 is fast.

These results are very troubling for those who deem threshold training to be the holy grail of training for distance running. But it’s important not to draw too extreme a conclusion from this study. The runners in the “easy” group trained pretty hard, and those in the “threshold” group arguably trained foolishly hard, even by the standards of most representatives of the high-intensity school. Take a closer look at those numbers in the “threshold” training regimen: 24.5 percent of their weekly miles were run at threshold pace (plus another 8.5 percent at speed pace). I’ve never known of any runner who did such a high percentage of his or her training at such a high intensity level. Here’s an example of a week of training that fits this breakdown:

You probably don’t need me to tell you that there is one high-intensity workout too many in this week. Doing four high-intensity workouts per week in a moderate-mileage program for five months straight is just not very smart. I believe that the runners in the study who did so simply weren’t able to properly absorb all of that hard work and wound up slightly overtrained. Consequently, the runners on the “easy” training regimen actually got more out of their three hard workouts per week than the others got out of their four. I would not be at all surprised to learn that the runners on the “easy” schedule, because they were getting adequate recovery between hard workouts, began performing better than members of the “threshold” group in their high-intensity workouts after just a few weeks, such that the results of the second time trial surprised no one.

It’s understandable that the researchers who performed this experiment wanted to make the two training regimens sufficiently distinct that they could point to a clear cause for the disparate effects they produced. But if you ask me, the runners in the threshold group were really set up for failure. I would have bet my house on the “easy” regimen producing better results than the “threshold” regimen, because the latter lacked the balance that has proven most effective in the training of runners in the real world for many decades.

Nevertheless, the study provides solid validation for the notion that a modest amount of threshold training goes a long way. The take-home lesson is this: You’ll get as much fitness as you can get from threshold training with one hard session per week. Adding a second threshold workout will not give you any extra fitness and may actually inhibit your fitness development by causing you to accumulate fatigue that you carry from one threshold workout to the next, so that you don’t perform as well as you should in these workouts and therefore get less benefit from them.